A description has been given in the prior art, U.S. Pat. No. 5,099,028, of a process for the preparation of the same 4-amino-1,2,4-triazoles of formula (1) in which the reaction of the acid RCOOH with the hydrazine is carried out in the presence of an insoluble polymer containing acid functional groups, that is to say an ion-exchange resin.
For products of formula (1) in which R is H, that is to say 4-amino-1,2,4-triazole, the prior art makes it possible to obtain, after recrystallization from isopropanol, a yield of 85% and a purity of 99.5%, if the resin is not recycled, or a yield of 91% and a purity of 99.4%, if the resin is recycled (% by weight).